Luminescent compound emitting white light, illuminator and organic el element emitting white light

ABSTRACT

The objectives of this invention are to provide a luminescent compound capable of emitting white light by itself, and an illuminator and organic EL element that emit white light by the employment of the luminescent compound. The illuminator and the organic EL element are capable of emitting white light at a strong luminance for a long time. 
 
The luminescent compound is represented by the following formula (1) or (2):  
                 
The illuminator and the organic EL element comprise a substrate on which an electrode has been formed and a luminescent layer including the compound, said luminescent layer being placed on the substrate.

TECHNICAL FIELD

The present invention relates to a luminescent compound emitting whitelight, and an illuminator and an organic EL element emitting white lightthat utilize the luminescent compound. More particularly, this inventionrelates to a single luminescent compound capable of emitting white lightby itself at a high luminance, which luminescent compound has aquinacridone skeleton and therefore is solid and excellent inworkability. This invention also provides a long-life illuminator andorganic EL element emitting, at a high luminance, white light made froma single emitting material, which illuminator and element utilize atleast one of the luminescent compounds of the invention for the emittingmaterial.

BACKGROUND ART

Conventional illuminators and organic EL elements emitting white lighthave, between a pair of electrodes, a light-emitting layer comprising acompound emitting red light (R), a compound emitting green light (G) anda compound emitting blue light (B). The white light was made through themixing of the three lights from the three compounds.

However, it was difficult to adjust the balance of the colors made bythe three different compounds. Besides, the compound emitting red lighttends to deteriorate. Therefore even though an illuminator or organic ELelement emits white light immediately after the production that hasincluded the step of adjusting the balance of the colors, theilluminator or element emits a colored light with the lapse of time,since the compound emitting red light deteriorates quickly. Anotherproblem of the conventional illuminator or element emitting white lightis that the luminance is low. On the other hand, few compounds that emitwhite light by themselves are known. In addition, conventional suchcompounds had only a short life, which was undesirable.

An objective of this invention is to provide a luminescent compoundemitting white light by itself, which can be used for an illuminator andorganic EL element emitting white light. In other words, this inventionis to provide a luminescent compound emitting white light that may beused for various white light-emitting bodies including an illuminator ororganic EL element. Conventional white light-emitting compounds weremade to emit white light by mixing pigments that respectively emit thethree primary colors, i.e. red, green and blue, and other pluralpigments. In this invention, however, is synthesized a new compoundcapable of emitting white light by itself, which compound can be adaptedto an organic EL element that emits pure white light at a high luminanceand has a long life.

Another objective of this invention is to provide, by utilizing thecompound emitting white light by itself, an illuminator and an organicEL element emitting white light by the light-emission of the singlecompound, which illuminator and organic EL element have a long life sothat they can emit white light for a long time. Still another objectiveof this invention is to provide a planar white light-emittingilluminator and a tubular white light-emitting illuminator utilizing thelong-life compound emitting white light by itself, which planar andtubular white light-emitting illuminators therefore can emit white lightfor a long time.

SUMMARY OF THE INVENTION

In order to solve the aforementioned problems, this invention provides aluminescent compound emitting white light that has a structurerepresented by formula (1):

wherein R¹ is hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; R² is hydrogen atom, an alkyl group,or an aryl or alkyl aryl group that may have at least one substituent,wherein two R²s may be the same or different from each other; and R¹ andR² may be the same or different from each other.

Alternatively, this invention provides a luminescent compound emittingwhite light that has a structure represented by formula (2):

wherein R¹ is hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; each of R³ and R⁴ is hydrogen atom,an alkyl group, or an aryl or alkyl aryl group that may have at leastone substituent, wherein R³ and R⁴ may be the same or different fromeach other; and two R³s may be the same or different and two R⁴ s may bethe same or different.

As another means to solve the aforementioned problems, this inventionprovides an illuminator emitting white light comprising a substrate onwhich an electrode is formed and a light emitting layer which is placedon the substrate, and a light emitting layer comprising a compoundemitting white light selected from the group consisting of a first whitelight-emitting compound represented by formula (1) and a second whitelight-emitting compound represented by formula (2), wherein each of thecompounds emits white light by itself.

In a preferred embodiment of this invention, the illuminator emittingwhite light is a one-layer type organic EL element comprising thesubstrate and the light emitting layer which comprises a compoundemitting white light selected from the group consisting of the firstwhite light-emitting compound represented by formula (1) and the secondwhite light-emitting compound represented by formula (2), wherein eachof the compounds emits white light by itself.

In another preferred embodiment of this invention, the illuminator is amulti-layer type organic EL element comprising the substrate, ahole-transporting layer, the light emitting layer which comprises aluminescent compound emitting white light selected from the groupconsisting of the first white light-emitting compound represented byformula (1) and the second white light-emitting compound represented byformula (2), and an electron-transporting layer. The light-emittinglayer may be a layer prepared by dispersing the compound emitting whitelight in a high polymer matrix, or by depositing the compound on thesubstrate. The illuminator may be a planar white light-emittingilluminator or a tubular white light-emitting illuminator.

As still another means to solve the aforementioned problems, thisinvention provides an organic EL element emitting white light comprisinga substrate on which an electrode is formed and a light-emitting layerwhich is placed on the substrate, and the light-emitting layer whichcomprises a compound emitting white light selected from the groupconsisting of a first white light-emitting compound represented byformula (1) and a second white light-emitting compound represented byformula (2), wherein each of the compounds emits white light by itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing a layer structure of the whitelight-emitting illuminator, which is an example of this invention.

FIG. 2 is an illustration showing another layer structure of the whitelight-emitting illuminator, which is another example of this invention.

FIG. 3 is an illustration showing still another layer structure of thewhite light-emitting illuminator, which is still another example of thisinvention.

FIG. 4 is an illustration showing a further layer structure of the whitelight-emitting illuminator, which is a further embodiment of thisinvention.

FIG. 5 is an IR chart of the compound prepared by the dehydrationreaction of dimethyl-1,4-cyclohexanedion-2,5-dicarboylate and3-amino-9-ethylcarbazole in Example 1.

FIG. 6 is an IR chart of the intermediate obtained by dehydrogenatingthe compound prepared by the dehydration reaction in Example 1.

FIG. 7 is an NMR chart of the intermediate obtained through thedehydrogenation in Example 1.

FIG. 8 is an IR chart of the white light-emitting compound prepared by aring-closing reaction in Example 1.

FIG. 9 is an NMR chart of the white light-emitting compound prepared inExample 1.

FIG. 10 is a fluorescent spectrum of the white light-emitting compoundprepared in Example 1.

FIG. 11 is an IR chart of the compound prepared by the dehydrationreaction of dimethyl-1,4-cyclohexanedion-2,5-dicarboxylate and2-amino-florene in Example 2.

FIG. 12 is an IR chart of the intermediate obtained by dehydrogenatingthe compound prepared by the dehydration reaction in Example 2.

FIG. 13 is an IR chart of the white light-emitting compound prepared bya ring-closing reaction in Example 2.

FIG. 14 is an IR chart of the compound having the structure representedby formula (16).

FIG. 15 is an IR chart of the compound having the structure representedby formula (1b).

FIG. 16 is a graph of spectral radiance showing the luminescentproperties of an organic EL element including the compound having thestructure represented by formula (1b).

FIG. 17 is a graph of spectral radiance showing the luminescentproperties of another organic EL element including the compound havingthe structure represented by formula (1b)

FIG. 18 is an IR chart of the compound having the structure representedby formula (21).

FIG. 19 is an IR chart of the compound having the structure representedby formula (1d).

FIG. 20 is a graph of spectral radiance showing the luminescentproperties of the organic EL element including the compound having thestructure represented by formula (1d).

FIG. 21 is a spectrum chart showing a typical emission spectrum andfluorescent spectrum of the luminescent compound emitting white light inaccordance with the invention.

FIG. 22 is an IR chart of the compound having the structure representedby formula (19).

FIG. 23 is an IR chart of the compound having the structure representedby formula (1c).

FIG. 24 is an IR chart of the liver brown powder obtained in Example 9.

FIG. 25 is an IR chart of the brown powder obtained in Example 9.

FIG. 26 is an IR chart of the liver brown powder obtained in Example 10.

FIG. 27 is an IR chart of the brown powder obtained in Example 10.

FIG. 28 is an IR chart of the liver brown powder obtained in Example 11.

FIG. 29 is an IR chart of the brown powder obtained in Example 11.

FIG. 30 is an IR chart of the liver brown powder obtained in Example 12.

FIG. 31 is an IR chart of the brown powder obtained in Example 12.

FIG. 32 is an IR chart of the liver brown powder obtained in Example 13.

FIG. 33 is an IR chart of the brown powder obtained in Example 13.

FIG. 34 is an IR chart of the liver brown powder obtained in Example 14.

FIG. 35 is an IR chart of the brown powder obtained in Example 14.

FIG. 36 is an IR chart of the liver brown powder obtained in Example 15.

FIG. 37 is an IR chart of the brown powder obtained in Example 15.

FIG. 38 is an IR chart of the blue brown powder obtained in Example 16.

FIG. 39 is an NMR chart of the blue brown powder obtained in Example 16.

FIG. 40 is an IR chart of the compound represented by formula (1e),which is the product synthesized in Example 16.

FIG. 41 is an NMR chart of the compound represented by formula (1e),which is the product synthesized in Example 16.

FIG. 42 is a graph showing a fluorescent spectrum of the compoundemitting white light represented by formula (1e), which is the productobtained in Example 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compound emitting white light in accordance with the presentinvention is a novel one represented by formula (1) or (2):

Each of the compounds respectively represented by formulae (1) and (2)has a quinacridone skeleton represented by formula (3):

The compound represented by formula (3) is well known as a pigmentcalled quinacridone or pigment violet 19. Quinacridone is synthesizedfrom diethyl succinyl succinate and aniline, both of which are the mainreactants, by, for example, condensation, ring closure and oxidation.Quinacridone per seis excellent in fastness, weatherability and heatresistance. (An excerpt from page 402 of “Shikisai Kogaku Handbook”, or“Handbook of Color Technology”, edited by Coloring Material Association,Co.)

The white light-emitting compound represented by formula (1) or (2) hasa quinacridone skeleton and a carbazole skeleton or carbazole-likeskeleton.

Therefore, the white light-emitting compound represented by formula (1)or (2), since it has a skeleton that is solid as a chemical structure,is excellent in fastness, weatherability, light stability and heatresistance. This compound, which has a quinacridone skeleton and acarbazole skeleton or carbazole-like skeleton, is a completely novelcompound, which is also excellent in luminescent properties andstructural stability.

In formula (1), R¹ denotes hydrogen atom, an alkyl group, or an aryl oralkyl aryl that may have at least one substituent. Suitable for thealkyl group are those having 1-30 carbon atoms, preferably 1-20 carbonatoms, more preferably 1-10 carbon atoms. In particular, a lower alkylgroup having 1-5 carbon atoms such as methyl group, ethyl group orpropyl group is preferable. Two R¹s may be the same or different fromeach other. When R¹ is an aryl group, it includes phenyl group, anaphthyl group, an anthryl group and a biphenyl group, and groupsderived from these aromatic groups by replacing at least one hydrogenatom thereof with a substituent such as an alkyl group or an alkoxygroup. When R¹ is an arylalkyl group, it includes benzyl group,1-phenylethyl group, 2-phenylethyl group, 1-phenylpropyl group,2-phenylpropyl group, 3-phenylpropyl group, 5-phenylbutyl group, etc.The phenyl moiety of these groups may further have substituents such asan alkyl group and alkoxyl group. The preferable arylalkyl group isbenzyl group.

In formula (1), each of two R²s is hydrogen atom, an alkyl group, or anaryl or arylalkyl group that may have at least one substituent. Two R²smay be the same or different from each other. Suitable for the alkylgroup are those having 1-30 carbon atoms, preferably 1-20 carbon atoms,more preferably 1-10 carbon atoms. In particular, a lower alkyl grouphaving 1-5 carbon atoms such as methyl group, ethyl group or propylgroup is preferable. Two R²s may be the same or different from eachother. When R² is an aryl group, it includes phenyl group, a naphthylgroup, an anthryl group and a biphenyl group, and groups derived fromthese aromatic groups by replacing at least one hydrogen atom thereofwith a substituent such as an alkyl group and an alkoxy group. Anexample of the derivative is p-alkoxyphenyl. When R² is an arylalkylgroup, it includes benzyl group, 1-phenylethyl group, 2-phenylethylgroup, 1-phenylpropyl group, 2-phenylpropyl group, 3-phenylpropyl group,5-phenylbutyl group, etc. The phenyl moiety of these groups may furtherhave substituents such as an alkyl group and alkoxyl group. Thepreferable arylalkyl group is benzyl group.

In formula (2), R¹ denote the same atom or group as that explained inrespect of formula (1).

In formula (2), each of R³ and R⁴ denotes hydrogen atom, an alkyl group,or an aryl or arylalkyl group that may have at least one substituent. R³and R⁴ may be the same or different from each other. Suitable for thealkyl group are those having 1-30 carbon atoms, preferably 1-20 carbonatoms, more preferably 1-10 carbon atoms. In particular, a lower alkylgroup having 1-5 carbon atoms such as methyl group, ethyl group orpropyl group is preferable. One of two R³s may be the same as the otherR³, or the former may be different from the latter. Two R⁴s may be thesame, or different from the latter. When R³ or R⁴ is an aryl group, itincludes phenyl group, a naphthyl group, an anthryl group and a biphenylgroup, and groups derived from these aromatic groups by replacing atleast one hydrogen atom thereof with a substituent such as an alkylgroup and an alkoxy group. An example of the derivative is p-alkoxyphenyl. When R³ or R⁴ is an arylalkyl group, it includes benzyl group,1-phenylethyl group, 2-phenylethyl group, 1-phenylpropyl group,2-phenylpropyl group, 3-phenylpropyl group, 5-phenylbutyl group, etc.The phenyl moiety of these groups may further have substituents such asan alkyl group and alkoxyl group. The preferable arylalkyl group isbenzyl group.

Substituents R¹, R², R³ and R⁴ provide the white light-emitting compoundrepresented by formula (1) or (2) with improved solubility in a solvent,which, in turn, enhances coating properties when the compound isdissolved in a suitable solvent. Also, these substituents lower thesublimation temperature of the compound, which improves operability inthe deposition. Furthermore, the compatibility of the compound with highpolymers is improved, which enables the compound to be included in ahigh polymer film.

The compound emitting white light may be produced in accordance with,for example, the following reaction formula.

In the reaction formula, R is a lower alkyl group, and R¹ and R² denotethe same atoms or groups as those explained above. The reactionproceeds, for example, by heating, in a solvent, dialkyl2,5-dihydroxy-1,4-cyclohexadiene-1,4-dicarboxylate, which corresponds toa compound represented by chemical formula (4), and such a compound as3-amino-9-alkylcarbazole, which corresponds to a compound represented bychemical formula (5). In the presence of a catalyst such as acetic acid,the dehydration reaction takes place, which produces the compound havingparts bonded by amino groups. This compound is shown by chemical formula(6).

When the dehydrated compound, obtained in the reaction above, is treatedwith such a dehydrating agent as a concentrated sulfuric acid, thedehydrogenation reaction shown by the following reaction formula takesplace.

When R¹ is hydrogen atom, the intermediate obtained by thedehydrogenation reaction can be alkylated through the reaction thereofwith a halogenated R¹ in, for example, DMF.

Then, the ring-closing reaction in accordance with the followingreaction formula is carried out.

The ring-closing reaction proceeds by heating the intermediate in asolvent, preferably in an inert organic solvent having a high boilingtemperature, such as dichlorobenzene, in the presence of an organic acidcatalyst such as p-toluenesulfonic acid. After the ring-closing reactionis obtained a white light-emitting compound that includes carbazoleskeletons represented by structural formula (8) above.

A compound shown by structural formula (8) is the white light-emittingcompound of this invention, the same as that represented by formula (1).

When a compound represented by formula (9) is employed in place of thatrepresented by formula (5), the white light-emitting compoundrepresented by formula (2) is obtained.

In formula (9), R¹, R³ and R⁴ are the same as those definedhereinbefore.

The reaction between dialkyl2,5-dihydroxy-1,4-cyclo-hexadiene-1,4-dicarboxylate, which is a compoundrepresented by chemical formula (4), and a compound represented byformula (9), such as 2-amino florene, proceeds by heating them in asuitable solvent. To subject the reaction product to the dehydrogenationand the ring closure leads to the production of a white light-emittingcompound of the invention, represented by formula (2).

Upon the application of electromagnetic energy, the white light-emittingcompound of this invention emits light that has the luminescent spectrarespectively corresponding to red, green and blue. The compound emitsvisible light of which wavelengths range between 400 nm and 700 nm, andtypically has such an emission spectrum and fluorescent spectrum asshown in FIG. 21. This compound can be utilized for an illuminator ororganic EL element capable of emitting white light.

FIG. 1 is an illustration showing a layer structure of the whitelight-emitting illuminator. As shown in FIG. 1, a white light-emittingilluminator A comprises a substrate 1 on which a transparent electrode 2is formed, a light-emitting layer 3 which is placed on the substrate 1,and an electrode layer 4 which is placed on the light-emitting layer 3.When the substrate has a planar shape, the white light-emittingilluminator A will be a planar luminescent illuminator. On the otherhand, when the substrate 1 in FIG. 1 is shaped into a tube, the whitelight-emitting illuminator A will be a tubular luminescent illuminator,such as a fluorescent tube. This tubular luminescent illuminator maytake the shape of either of a straight tube or a ring tube, such as“CIRCLINE”.

For the substrate 1 may be used any known substrate, as long as thetransparent electrode 2 can be formed on the surface of the substrate.Examples of the substrate 1 are a glass substrate, a plastic sheet, aceramic substrate, and a metal substrate of which surface is insulated,for example, through the formation of an insulating layer thereon. Whenthe substrate 1 is opaque, the white light-emitting illuminator is asingle-faced one that emits white light from one side of the substrate.On the other hand, when the substrate 1 is transparent, the illuminatoris a double-faced one that emits white light from both sides of thesubstrate.

For the transparent electrode 2, various materials may be employed, aslong as their work functions are large, they are transparent, and theycan function as a cathode and inject holes into the light-emitting layer3 when voltage is applied thereto. Specifically, the transparentelectrode 2 may be made of a transparent inorganic conductive materialof ITO, In₂O₃, SnO₂, ZnO, CdO, etc. and derivatives thereof, or anelectrically conductive high polymer such as polyaniline.

The transparent electrode 2 may be formed on the substrate 1 by chemicalvapor phase growth, spray pyrolysis, high-vacuum metal deposition,electron beam deposition, sputtering, ion beam sputtering, ion plating,ion-assisted deposition, and other methods.

When the substrate is made of an opaque material, the electrode formedon the substrate need not be transparent.

The light-emitting layer 3 is a layer that includes a special whitelight-emitting compound of the invention. The white light-emittingcompound, will be explained hereinafter. The light-emitting layer 3 maybe a high polymer film where the white light-emitting compound isdispersed in a high polymer. The layer may also be a deposited filmprepared by depositing the white light-emitting compound on thetransparent electrode 2.

Examples of the high polymer for the high polymer film are a polyvinylcarbazole, a poly(3-alkylthiophen), a polyimide including an arylamide,a polyfluorene, a polyphenylene vinylene, a poly-α-methylstyrene, acopolymer of vinyl-carbazole and α-methylstyrene. Of them, a polyvinylcarbazole is preferable.

The amount of the white light-emitting compound included in the highpolymer film is, typically, 0.01-2 weight %, preferably, 0.05-0.5 weight%.

The thickness of the high polymer film ranges, typically, between 30 nmand 500 nm, preferably between 100 nm and 300 nm. When the thickness istoo small, the amount of the emitted light may be insufficient. On theother hand, when the thickness is too large, the voltage required todrive the illuminator or element may be too high, which is notdesirable. Besides, the large thickness may reduce the flexibility ofthe film necessary to shape a planar, tubular, curved or ring article.

The high polymer film may be formed through the application of asolution of the high polymer and the white light-emitting compound ofthe invention dissolved in a suitable solvent. The application method isone selected from a spin cast method, a coating method, a dippingmethod, etc.

When the light-emitting layer 3 is a deposited film, the thickness ofthe film is generally 0.1-100 nm, although a preferable thickness isdifferent depending on the structure of layers and other factors. Whenthe thickness is too large or too small, it might cause the sameproblems as described above.

For the electrode layer 4 may be employed a material having a small workfunction. Examples of the material are elementary metals and metallicalloys, such as MgAg, aluminum alloy, metallic calcium, etc. Apreferable electrode layer 4 is made of an alloy of aluminum and a smallamount of lithium. This electrode may easily be formed on the surface ofthe light-emitting layer 3, which, in turn, has been formed on thesubstrate 1, by the technique of metal deposition.

When either of the deposition or the application is employed, a bufferlayer should be inserted between the electrode layer and thelight-emitting layer.

Materials for the buffer layer are, for example, an alkaline metalcompound such as lithium fluoride, an alkaline earth metal compound suchas magnesium fluoride, an oxide such as an aluminum oxide, and4,4′-biscarbazole biphenyl (Cz-TPD). Also, materials for forming thebuffer layer between the cathode made of ITO, etc. and the organic layerare, for example, m-MTDATA(4,4′,4″-tris(3-methylphenyl-phenylamino)triphenylamine),phthalocyanine, a polyaniline, a polythiophene derivative, and inorganicoxides such as molybdenum oxide, ruthenium oxide, vanadium oxide andlithium fluoride. When the materials are suitably selected, these bufferlayers can lower the driving voltage of the organic EL element, which isa white light-emitting illuminator, improve the quantum efficiency ofluminescence, and achieve an increase in the luminance of the emittedlight.

The white light-emitting illuminator shown in FIG. 1, which includes thesingle luminescent compound capable of emitting white light in thelight-emitting layer, emits white light, when an electric current isapplied via the transparent electrode 2 and the electrode layer 4.

The following is the explanation for the phenomenon of luminescence.When an electric field is applied to the layer between the transparentelectrode 2 and the electrode layer 4, electrons are injected into thelayer from the electrode layer 4 and positive holes are injected intothe layer from the transparent electrode 2. In the light-emitting layer3, the electrons are recombined with positive hole, which causes theenergy level to return to the valence band from the conduction band.This transition of the energy level is accompanied by emission of theenergy differential as light.

The white light-emitting illuminator A shown in FIG. 1, when it isshaped into a planar one with a large area, may be used as a large-areawall illuminator fixed on a wall or a large-area ceiling illuminatorfixed on a ceiling. This white light-emitting illuminator may be used asa planar light source in place of a point light source, such as aconventional bulb, and a line light source, such as a conventionalfluorescent lamp. In particular, this white light-emitting illuminatorcan suitably be used to light up walls and ceilings in dwelling rooms,offices and passenger trains, or to make them emit light. Moreover, thisilluminator may be suitable for the backlight used in the displays ofcomputers, cellular phones and ATMs. Furthermore, this illuminator maybe used for various light sources, such as the light source of directillumination and that of indirect illumination. Also, because it canemit light at night and provide good visibility, it may be used for thelight sources of advertisement apparatuses, road traffic signapparatuses, light-emitting billboards and stop lamps of vehicles. Inaddition, because the white light-emitting illuminator A includes thewhite light-emitting compound, which has the special chemical structure,in the light-emitting layer, the illuminator has a long life. Therefore,light sources employing the white light-emitting illuminator A willnaturally have a long life.

The white light-emitting illuminator A may also be shaped into a tubularlight emitter comprising a tubularly shaped substrate 1, a transparentelectrode 2 placed on the inside surface of the substrate 1, a lightemitting layer 3 and an electrode layer 4 placed on the transparentelectrode 2 in this order. Because this illuminator does not includemercury, it is an ecological light source and may be a substitute forconventional fluorescent lamps.

Another example of the white light-emitting illuminator in accordancewith this invention is shown in FIG. 2. This figure is an illustrationshowing the layer structure of an example of the white light-emittingilluminator, which is a multi-layer organic EL element.

As shown in FIG. 2, a white light-emitting illuminator B comprises asubstrate 1, and a transparent electrode 2, a hole-transporting layer 5,a light-emitting sub layers 3 a, 3 b and 3 c, an electron-transportinglayer 6, and an electrode layer 4, the layers being laid on thesubstrate 1 one layer by one layer in this order.

The substrate 1, the transparent electrode 2 and the electrode layer 4are the same as those explained for the illuminator A in FIG. 1.

The light-emitting layer of the illuminator B comprises light-emittingsub layers 3 a and 3 b. The light-emitting sub layer 3 a is a depositedfilm including the white light-emitting compound of this invention. Thelight-emitting sub layer 3 b is a DPVBi layer, which functions as a hostmaterial.

Examples of the hole-transporting substance included in thehole-transporting layer 5 are a triphenylamine compound such asN,N′-diphenyl-N,N′-di(m-tolyl)-benzidine (TPD) and α-NPD, a hydrazoncompound, a stilbene compound, a heterocyclic compound, a π electronstar burst positive hole transporting substance, etc.

Examples of the electron-transporting substance included in theelectron-transporting layer 6 are an oxadiazole derivative such as2,5-bis(1-naphthyl)-1,3,4-oxadiazole (BND) and2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole, and2,5-bis(5′-tert-butyl-2′-benzoxazolyl)-thiophene. Also, a metal complexmaterial such as quinolinol aluminum complex (Alq3), benzoquinolinolberyllium complex (Bebq2) can be used suitably.

The white light-emitting illuminator B shown in FIG. 2 employs Alq3 aselectron-transporting substance in the electron-transporting layer 6.

The thickness of each layer is the same as that in a known multi-layerorganic EL element.

The illuminator B in FIG. 2 functions and emits light in the same waysas the illuminator A in FIG. 1. Therefore, the illuminator B has thesame uses as the illuminator A.

The third example of the white light-emitting illuminator of thisinvention is shown in FIG. 3. This figure is an illustration showing thesectional layer structure of an example of the white light-emittingilluminator, which is a multi-layer organic EL element.

As shown in FIG. 3, a white light-emitting illuminator C comprises asubstrate 1, and a transparent electrode 2, a hole-transporting layer 5,a light-emitting layer 3, an electron-transporting layer 8, and anelectrode layer 4, the electrode and layers being laid on the substrate1 one layer by one layer in this order.

The illuminator C functions in the same way as the illuminator B.

Another example of the white light-emitting illuminator of thisinvention is shown in FIG. 4. A white light-emitting illuminator Dcomprises a substrate 1, and a transparent electrode 2, ahole-transporting layer 5, a light-emitting layer 3, and an electrodelayer 4, the electrode and layers being laid on the substrate 1 onelayer by one layer in this order.

An example of the white light-emitting illuminators other than thoseshown in FIGS. 1-4, is a two-layer low molecular weight organicluminescent element having a hole-transporting layer that includes ahole-transporting substance and an electron-transporting luminescentlayer that includes the white light-emitting compound of the inventionlaid on the hole-transporting layer, these layers sandwiched between acathode, which is a transparent electrode formed on the substrate, andan anode, which is an electrode layer. A specific example of thisembodiment is a two-layer pigment-injected luminescent elementcomprising a hole-transporting layer and a luminescent layer thatincludes a host pigment and the white light-emitting compound of thisinvention as a guest pigment, wherein the luminescent layer is laid onthe hole-transporting layer and these layers are sandwiched between thecathode and the anode. Another example is a two-layer organicluminescent element comprising a hole-transporting layer that includes ahole-transporting substance and an electron-transporting luminescentlayer that is prepared through a co-deposition of the whitelight-emitting compound and an electron-transporting substance, thelatter layer being laid on the former, and these two layers beingsandwiched between the cathode and the anode. A specific example of thesecond embodiment is a two-layer pigment-injected luminescent elementcomprising a hole-transporting layer and an electron-transportingluminescent layer that includes a host pigment and the whitelight-emitting compound of this invention as a guest pigment, whereinthe luminescent layer is laid on the hole-transporting layer and theselayers are sandwiched between the cathode and the anode. A furtherexample is a three-layer organic luminescent element comprising ahole-transporting layer, a luminescent layer including the whitelight-emitting compound of this invention that is laid on thehole-transporting layer, and an electron-transporting layer that is laidon the luminescent layer, these layers being sandwiched between thecathode and the anode.

The electron-transporting luminescent layer, typically, comprises 50-80weight % of polyvinylcarbazole, which is abbreviated to PVK, 5-40 weight% of an electrode-transporting luminescent agent, and 0.01-20 weight %of the white light-emitting compound of this invention. Theelectron-transporting luminescent layer of this composition is capableof emitting white light at a high luminance.

Also, it is preferable, if the luminescent layer includes, as asensitizing agent, rubrene, especially both of rubrene and Alq3.

A white light-emitting illuminator utilizing the compound of thisinvention may generally be used as an organic EL element which isdriven, generally, by direct current, and also by pulses and alternatingcurrent.

EXAMPLES Working Example 1

<Dehydration Reaction>

In a 1000 ml three-necked flask were placed 25.0 g (1.2×10⁻¹ mol) of3-amino-9-ethylcarbazole, 15.4 g (6.0×10⁻² mol) of the compoundrepresented by formula (10), 200 ml of acetic acid and 200 ml of ethylalcohol.

The mixture was placed in a silicone oil bath and heated to 120° C. withstirring. The reaction was allowed to continue for 4 hours. After thetermination of the reaction, the mixture was cooled to the roomtemperature.

The obtained reaction mixture was filtered with a glass filter. Solidmatter remaining on the filter was washed with methyl alcohol that hadbeen cooled to 5° C. and petroleum ether in this order. The washed solidmatter was dried in a vacuum. 35.2 g of terracotta powder was obtained.

An IR chart of the powder is shown in FIG. 5. This terracotta powder wasa compound represented by formula (11).

<Dehydrogenation Reaction>

In a 1000 ml three-necked flask, 25.0 g of the powder produced in thedehydration reaction was placed and 500 ml of o-dichlorobenzene wasadded thereto. 1.0 g of 95% sulfuric acid was gradually dripped into theflask and stirred for 30 minutes. The mixture was heated to 160° C. withstirring in a silicone oil bath and allowed to react for 2 hours. Afterthe termination of the reaction, the reacted mixture was cooled to theroom temperature and then introduced into ice water.

The obtained mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was carried out three times. Theextract was washed with water twice and then the moisture includedtherein was removed with sodium sulfate. The washed and dried wasfiltered, concentrated and dried up with an evaporator. The obtainedsolid was washed with acetic acid and petroleum ether in this order, anddried in a vacuum. 13.1 g of red powder was obtained.

An IR chart of the red powder is shown in FIG. 6 and an NMR chartthereof is shown in FIG. 7. This red powder had the chemical structurerepresented by following formula (12).

<Ring-Closing Reaction>

In a 500 ml three-necked flask were placed 10.0 g (1.6×10⁻² mol) of thered powder, 13.7 g (7.2×10⁻² mol) of hydrated p-toluenesulfonic acid,and 200 ml of o-dichlorobenzene. The mixture was placed in a siliconeoil bath and heated to 160° C. with stirring. The reaction was allowedto continue for 20 hours. After the termination of the reaction, thereacted mixture was concentrated and dried up with an evaporator. Theobtained solid was washed with methyl alcohol that had been cooled to 5°C., acetone, and petroleum ether in this order, and then vacuum dried.9.4 g of brown powder was obtained. In order to purify the powder, 700ml of xylene was placed in a 1000 ml Erlenmeyer flask, and 2.0 g of thebrown powder and 2.0 g of activated carbon were added to the xylene. Themixture was boiled for 3 minutes with a mantle heater. While the mixturewas hot, the liquid was filtered. Then, the obtained filtrate wasconcentrated and dried up with an evaporator.

The dry solid was washed with petroleum ether, and dried in a vacuum.Reddish-brown powder was obtained. An IR chart of the reddish-brownpowder is shown in FIG. 8, and an NMR chart thereof in FIG. 9.

This reddish-brown powder was a compound having the chemical structurerepresented by formula (1a) below.

(Preparation of White Light-Emitting Illuminator)

In a 5 ml graduated flask were placed 70 mg of polyvinylcarbazole, 29.7mg of t-butylphenyl-diphenyl-1, 3,4-oxadiazole (PBD) and 0.3 mg of thereddish-brown powder, which is the compound represented by formula (1a).Dichloroethane was added to the flask so that the total volume of themixture was 5 ml. Thus, a solution including the white light-emittingcompound was prepared. This solution was sufficiently homogenized byirradiating it with ultrasound for 20 minutes using a model US-2ultrasonic cleaner, a product by M.D. Excimer, Inc. An ITO substrate, aproduct by Sanyo Shinku Industries, Co., Ltd., of which dimensions were50×50 mm and thickness as a transparent electrode was 200 μm, wasultrasonically cleaned in acetone for 10 minutes and then in 2-propanolfor 10 minutes. The substrate was blow-dried with nitrogen. Then, thesubstrate was cleaned by ultraviolet-light irradiation for 30 seconds ata wavelength of 172 nm with a UV irradiator produced by M.D. Excimer,Inc. The solution containing the white light-emitting luminescentcompound, which had been prepared, was dropped onto the obtained ITOsubstrate and a film was formed on the surface of the substrate byspin-coating at 1,500 rpm for 3 seconds with a model 1H-D7 spin coater,a product by Mikasa Co., Ltd., so that the thickness of the film was 100μm when it was dried. The substrate with the film was dried for 30minutes in a constant temperature bath at 50° C. The electrode of analuminum alloy, a product by Kojundo Chemical Laboratory, Co., Ltd., inwhich the weight ratio of Al to Li was 99:1, was deposited on thesubstrate under 4×10⁻⁶ Torr with a vacuum metallizer (Model VDS-M2-46,produced by DIAVAC Limited). The thickness of the electrode was about150 nm. Thus a white light-emitting illuminator having a structure shownin FIG. 1 was obtained.

The luminance and the chromaticity of the illuminator were measured witha Fast BM-7 measuring apparatus produced by TOPCON Corporation, with thevoltage being raised gradually. The results were that, when the voltagewas 21 V and the current was 9.69 mA, the luminance was 2,300 Cd/m²,chromaticity X 0.33, and chromaticity Y 0.33.

<Luminescent Properties>

A sample solution was prepared by dissolving the white light-emittingcompound represented by formula (1a) in mixed xylene, so that theconcentration of the compound was 10 mg/L. This sample solution wasloaded in a model F-4500 spectrofluorophotometer, a product by ShimadzuCorporation, and the fluorescence spectrum of the solution was measuredunder the following conditions. The measured spectrum is shown in FIG.10.

Conditions of Measurement

-   Measuring mode: Wavelength scanning-   Exciting wavelength: 365 nm-   Wavelength at which the emission of fluorescence started: 400 nm-   Wavelength at which the emission of fluorescence ended: 700 nm-   Scanning speed: 1200 nm/min.-   Slit on the side of excitation: 5.0 nm-   Slit on the side of fluorescence emission: 5.0 nm-   Photomal voltage: 700 V

As understood from FIG. 10, the fluorescence of the white light-emittingcompound obtained in this example covers a visible light range of whichwavelengths are from 400 nm to 700 nm.

Working Example 2

<Dehydration Reaction>

In a 1000 ml three-necked flask were placed 25.0 g (1.4×10⁻¹ mol) of2-amino-florene represented by formula (13), 17.9 g (7.0×10⁻² mol) ofthe compound represented by formula (10), 200 ml of acetic acid, and 200ml of ethyl alcohol.

The mixture was placed in a silicone oil bath and heated to 120° C. withstirring. The reaction was allowed to continue for 4 hours. After thetermination of the reaction, the mixture was cooled to the roomtemperature.

The obtained reaction mixture was filtered with a glass filter. Solidsremaining on the filter were washed with methyl alcohol that had beencooled to 5° C. and petroleum ether in this order. The washed solidswere dried in a vacuum. 35.4 g of orange powder was obtained.

An IR chart of the powder is shown in FIG. 11. This orange powder was acompound represented by formula (14).

<Dehydrogenation Reaction>

In a 1000 ml three-necked flask, 25.0 g of the orange powder produced inthe dehydration reaction was placed, and 500 ml of o-dichlorobenzene wasadded thereto. 1.0 g of 95% sulfuric acid was gradually dripped into theflask and stirred for 30 minutes. The mixture was heated to 160° C. withstirring in a silicone oil bath and allowed to react for 2 hours. Afterthe termination of the reaction, the reacted mixture was cooled to theroom temperature and then poured into ice water.

The obtained mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was carried out three times. Theextract was washed with water twice and then moisture included thereinwas removed with sodium sulfate. The washed and dried was filtered,concentrated and dried up with an evaporator. The obtained solid waswashed with acetic acid and petroleum ether in this order, and dried ina vacuum. 20.5 g of red powder was obtained.

An IR chart of the red powder is shown in FIG. 12. This red powder hadthe chemical structure represented by following formula (15).

<Ring-Closing Reaction>

In a 500 ml three-necked flask were placed 10.0 g (1.7×10⁻² mol) of thered powder, 15.3 g (8.0×10⁻² mol) of hydrated p-toluenesulfonic acid,and 200 ml of o-dichlorobenzene. The mixture was placed in a siliconeoil bath and heated to 160° C. with stirring. The reaction was allowedto continue for 20 hours. After the termination of the reaction, thereacted mixture was concentrated and dried up with an evaporator. Theobtained solid matter was washed with methyl alcohol that had beencooled to 5° C., acetone and petroleum ether in this order, and thenvacuum dried. 8.2 g of brown powder was obtained. In order to purify thepowder, 700 ml of xylene was placed in a 1000 ml Erlenmeyer flask, and2.0 g of the brown powder and 2.0 g of activated carbon were added tothe xylene. The mixture was boiled for 3 minutes with a mantle heater.While the mixture was hot, the liquid was filtrated. Then, the obtainedfiltrate was concentrated and dried up with an evaporator.

The dry solids were washed with petroleum ether, and dried in a vacuum.Reddish-brown powder was obtained. An IR chart of the reddish-brownpowder is shown in FIG. 13.

This reddish-brown powder was a compound having the chemical structurerepresented by formula (2a) below.

Working Example 3

<Benzylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compoundrepresented by formula (12), the same compound as that obtained inWorking Example 1 was placed. 17.1 g (7.6×10⁻² mol) of benzyl bromideand 200 mol of N,N-dimethylformamide, which will be abbreviated to DMF,were added in this order to the compound. The mixture was heated to 150°C. in a silicone oil bath and allowed to react for 20 hours. After thetermination of the reaction, the bottle was cooled to the roomtemperature. Then, the reacted mixture was concentrated with anevaporator. The concentrated mixture was poured into ice water andfurther neutralized with sodium hydroxide. The neutralized mixture wassubjected to extraction with chloroform using a separatory funnel, andthe extraction was carried out three times. The extract was washed withwater twice and then moisture included therein was removed with sodiumsulfate. The washed and dried was filtered, and concentrated and driedup with an evaporator. The obtained solid matter was washed withpetroleum ether, and dried in a vacuum. Liver brown powder was obtained.

An IR chart of the liver brown powder is shown in FIG. 14. This liverbrown powder had the chemical structure represented by following formula(16).

<Ring-Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (6.1×10⁻³ mol) of thecompound represented by formula (16), 5.2 g (2.7×10⁻² mol) of hydratedp-toluenesulfonic acid, and 200 ml of o-dichlorobenzene. The mixture wasplaced in a silicone oil bath and heated to 160° C. with stirring. Thereaction was allowed to continue for 20 hours. After the termination ofthe reaction, the reacted mixture was concentrated and dried up with anevaporator. The obtained solids were washed with methyl alcohol that hadbeen cooled to 5° C., acetone and petroleum ether in this order, andthen vacuum dried. A brown solid matter was obtained.

1.0 g of the brown solid matter in 250 ml of xylene was extracted with aSoxhlet abstractor for 24 hours. After the completion of the extraction,the extract was concentrated and dried up with an evaporator. The driedsolid was washed with petroleum ether, and dried in a vacuum. Lightbrown powder was obtained. An IR chart of the light brown powder isshown in FIG. 15. This light brown powder was a compound having thechemical structure represented by formula (1b) below.

The steps described under the title of (Preparation of WhiteLight-emitting Illuminator) in Working Example 1 were repeated, exceptthe step of preparing the solution including 70 mg ofpolyvinylcarbazole, 29.7 mg of t-butylphenyl-diphenyl-1,3,4-oxadiazole(PBD), 0.3 mg of the reddish-brown powder, which is the compoundrepresented by formula (1a), and dichloroethane added so that the totalvolume of the mixture was 5 ml. In place of the above-mentioned step,the following was carried out: In a 5 ml graduated flask were placed 70mg of polyvinylcarbazole, 29.7 mg of BND having the structurerepresented by formula (17) and 0.3 mg of the white light-emittingcompound represented by formula (1b). Dichloroethane was added to theplaced so that the total volume of the mixture was 5 ml. Thus, asolution including the white light-emitting compound was prepared. Withthis solution, a white light-emitting illuminator having the structureshown in FIG. 1 was prepared in the same way as in Working Example 1.The luminance and the chromaticity of the illuminator were measured witha model SR-3 spectroradiometer produced by TOPCON Corporation.

The results were that, when the voltage was 21 V and the current was36.8 mA, the luminance was 2,400 Cd/m², chromaticity X 0.34, andchromaticity Y 35. A graph of the spectral radiance of this whitelight-emitting compound having been measured with the spectroradiometeris shown in FIG. 16. From this graph, it is understood that the color ofthe emitted light was sufficiently white to the naked eye.

<Luminescent Properties>

An ITO substrate, a product by Sanyo Shinku Industries, Co., Ltd., ofwhich dimensions were 50×50 mm and thickness as a transparent electrodewas 200 μm, was ultrasonically cleaned in acetone for 10 minutes andthen in 2-propanol for 10 minutes. The substrate was blow-dried withnitrogen. Then, the substrate was cleaned by ultraviolet-lightirradiation for 30 seconds at a wavelength of 172 nm with a UVirradiator produced by M.D. Excimer, Inc.

The obtained ITO substrate was set in a model USD-M2-46 vacuummetallizer, a product by DIAVAC Limited. With this apparatus,N,N′-diphenyl-N,N-di(m-tolyl)-benzidine, which will be abbreviated toTPD, was deposited on the substrate, so that the formed layer had athickness of 63 nm. Then, the white light-emitting compound representedby formula (1b) was deposited on the TPD layer so that the whitelight-emitting compound layer had a thickness of 0.5 nm. Next, DPVBihaving the structure represented by formula (18) was deposited on thecompound layer so that the DPVBi layer had a thickness of 35 nm.Furthermore, tris(8-quinolinate) aluminum (Alq3) was deposited on theDPVBi layer so that the Alq3 layer has a thickness of 150 nm. Finally,an electrode was made through the deposition of an aluminum alloy, aproduct by Kojundo Chemical Laboratory, Co., Ltd., in which the weightratio of Al to Li was 99:1, on the Alq3 layer. The thickness of theelectrode was 150 nm. All of the depositions were carried out under apressure of 4×10⁻⁶ Torr with the vacuum metallizer. Thus a whitelight-emitting illuminator having the structure shown in FIG. 2 wasobtained.

The luminance and the chromaticity of the illuminator were measured withthe same method as in Working Example 1.

The results were that, when the voltage was 17 V and the current was21.8 mA, the luminance was 4,500 Cd/m², chromaticity X 0.32, andchromaticity Y 0.35. Also, a graph of the spectral radiance of thiswhite light-emitting compound that was measured with thespectroradiometer is shown in FIG. 17. From this graph, it is understoodthat the color of the emitted light was sufficiently white to the nakedeye.

Working Example 4

A white light-emitting illuminator having the structure shown in FIG. 3was prepared. The preparation steps were the same as those in WorkingExample 3, except that the thickness of theN,N′-diphenyl-N,N-di(m-tolyl)-benzidine layer was 59 nm, that of thelayer of the white light-emitting compound was 0.7 nm, and that of theDPVBi layer was 36 nm. The luminescent properties of the obtainedilluminator were measured with the same method as in Working Example 3.The results were that, when the voltage was 20 V and the current was31.2 mA, the luminance was 3,100 Cd/m², chromaticity X 0.33, andchromaticity Y 0.34.

Working Example 5

On a transparent polyester film substrate having a thickness of 188 μm,an ITO electrode having a thickness of 200 nm was formed by deposition.On the surface of the ITO electrode, the first layer ofα-NPD(di-(naphtyl-phenylamino)diphenyl), the second layer of the whitelight-emitting compound having the structure represented by formula(1b), the third layer of DPVBi and the fourth layer of Alq3 were laid inthis order by deposition. The thickness of the first layer, that of thesecond layer, that of the third layer and that of the fourth layer were66 nm, 0.3 nm, 40 nm and 40 nm respectively. On the top of thislaminate, an electrode was made through the deposition of an aluminumalloy, a product by Kojundo Chemical Laboratory, Co., Ltd., in which theweight ratio of Al to Li was 99:1, on the fourth layer. The thickness ofthe electrode was 150 nm. Thus a white light-emitting illuminator havingthe structure shown in FIG. 2 was obtained. Note that light-emittinglayer 3 in FIG. 2 was made of the second and third layers.

The luminescent properties of the obtained illuminator were measuredwith the same method as in Working Example 3. As a result, when thevoltage was 16 V and the current was 22.6 mA, the luminance was 7,500Cd/m², chromaticity X 0.30, and chromaticity Y 0.37.

Working Example 6

A white light-emitting illuminator having the structure shown in FIG. 2was prepared. The preparation steps were the same as those in WorkingExample 5, except that the first layer was made of TPD, the second layerof the white light-emitting compound having the structure represented byformula (1a), the third layer of DPVBi and the fourth layer of Alq3. Thethickness of the first layer, that of the second layer, that of thethird layer and that of the fourth layer were 64 nm, 0.6 nm, 35 nm and38 nm respectively. Note that light-emitting layer 3 in FIG. 2 was madeof the second and third layers.

The luminescent properties of the obtained illuminator were measuredwith the method as in Working Example 3. As a result, when the voltagewas 14 V and the current was 27.9 mA, the luminance was 5,100 Cd/m²,chromaticity X 0.30, and chromaticity Y 0.33.

Working Example 7

<Methylbenzylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compoundrepresented by formula (12), the same compound as that obtained inWorking Example 1 was placed. 15.8 g (1.1×10⁻¹ mol) of α-chloro-p-xyleneand 200 ml of N,N-dimethylform-amide (DMF) were added in this order tothe compound. The mixture was heated to 150° C. in a silicone oil bathand allowed to react for 20 hours. After the termination of thereaction, the bottle was cooled to the room temperature. Then, thereacted mixture was concentrated with an evaporator. The concentratedmixture was poured into ice water and further neutralized with sodiumhydroxide. The neutralized mixture was subjected to extraction withchloroform using a separatory funnel, and the extraction was carried outthree times. The extract was washed with water twice and then moistureincluded therein was removed with sodium sulfate. The washed and driedwas filtered, and concentrated and dried up with an evaporator. Theobtained solid was washed with petroleum ether, and dried in a vacuum.Liver brown powder was obtained.

An IR chart of the liver brown powder is shown in FIG. 22. This liverbrown powder had the chemical structure represented by formula (19).

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (5.4×10⁻³ mol) of thecompound represented by formula (19), 8.0 g (4.1×10⁻² mol) ofp-toluenesulfonic acid monohydrate, and 200 ml of o-dichlorobenzene. Themixture was placed in a silicone oil bath and heated to 160° C. withstirring. The reaction was allowed to continue for 20 hours. After thetermination of the reaction, the reacted mixture was concentrated anddried up with an evaporator. The obtained solid was washed with methylalcohol that had been cooled to 5° C., acetone, and petroleum ether inthis order, and then vacuum dried. A brown solid matter was obtained.

1.0 g of the brown solid matter in 250 ml of xylene was extracted with aSoxhlet abstractor for 24 hours. After the completion of the extraction,the extract was concentrated and dried up with an evaporator. The driedsolids were washed with petroleum ether, and dried in a vacuum. Lightbrown powder was obtained. An IR chart of the light brown powder isshown in FIG. 23. This light brown powder was a compound having thechemical structure represented by formula (1c) below.

<White Light-Emitting Illuminator>

A white light-emitting illuminator having the structure shown in FIG. 3was prepared. The preparation steps were the same as those in WorkingExample 3, except that α-NPD, DPVBi doped with 4.4% of the whitelight-emitting compound having the structure represented by formula(1c), and Alq3 were deposited in this order. The thickness of the α-NPDlayer, that of the doped DPVBi layer, and that of the Alq3 layer were 45nm, 18 nm and 21 nm respectively.

The luminescent properties of the obtained illuminator were measuredwith the same method as in Working Example 3. The results were that,when the voltage was 18 V and the current was 30.9 mA, the luminance was10,720 Cd/m², chromaticity X 0.35, and chromaticity Y 0.39.

<White Light-Emitting Illuminator>

A white light-emitting illuminator having the structure shown in FIG. 3was prepared. The preparation steps were the same as those in WorkingExample 3, except that α-NPD, CBP, which is represented by formula (20)below, doped with 2.9% of the white light-emitting compound having thestructure represented by formula (1c), and Alq3 were deposited in thisorder. The thickness of the α-NPD layer, that of the doped CBP layer,and that of the Alq3 layer were 46 nm, 31 nm and 19 nm respectively.

The luminescent properties of the obtained illuminator were measuredwith the same method as in Working Example 3. The results were that,when the voltage was 17 V and the current was 36.1 mA, the luminance was10,120 Cd/m², chromaticity X 0.32, and chromaticity Y 0.35.

Working Example 8

<Methylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10² mol) of the compoundrepresented by formula (12), the same compound as that obtained inWorking Example 1 was placed. 10.8 g (7.6×10² mol) of iodomethane and200 ml of N,N-dimethylformamide (DMF) were added in this order to thecompound. The mixture was heated to 150° C. in a silicone oil bath andallowed to react for 20 hours. After the completion of the reaction, thebottle was cooled to the room temperature. Then, the reacted mixture wasconcentrated with an evaporator. The concentrated mixture was pouredinto ice water and further neutralized with sodium hydroxide. Theneutralized mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was carried out three times. Theextract was washed with water twice and then moisture included thereinwas removed with sodium sulfate. The washed and dried was filtered, andconcentrated and dried up with an evaporator. The obtained solid waswashed with petroleum ether, and dried in a vacuum. Liver brown powderwas obtained. An IR chart of the liver brown powder is shown in FIG. 18.This liver brown powder had the chemical structure represented byformula (21).

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (7.5×10⁻³ mol) of thecompound represented by formula (21), 8.0 g (4.2×10⁻² mol) ofp-toluenesulfonic acid monohydrate, and 200 ml of o-dichlorobenzene. Themixture was placed in a silicone oil bath and heated to 160° C. withstirring. The reaction was allowed to continue for 20 hours. After thetermination of the reaction, the reacted mixture was concentrated anddried up with an evaporator. The obtained solid was washed with methylalcohol that had been cooled to 5° C., acetone and petroleum ether inthis order, and then vacuum dried. A brown solid matter was obtained.

1.0 g of the brown solid matter in 250 ml of xylene was extracted with aSoxhlet abstractor for 24 hours. After the completion of the extraction,the extract was concentrated and dried up with an evaporator. The driedsolids were washed with petroleum ether, and dried in a vacuum. Lightbrown powder was obtained. An IR chart of the light brown powder isshown in FIG. 19. This light brown powder was a compound having thechemical structure represented by formula (1d) below.

<White Light-Emitting Illuminator>

An EL element was prepared in accordance with the method explained underthe subtitle <Luminescent Properties>of Working Example 3. On thesurface of the ITO electrode, the first layer of TPD, the second layerof the white light-emitting compound having the structure represented byformula (1d), the third layer of DPVBi and the fourth layer oftris(8-quinolinate)aluminum Alq3 were laid in this order by deposition.The thickness of the first layer, that of the second layer, that of thethird layer and that of the fourth layer were 71 nm, 0.6 nm, 40 nm and41 nm respectively. On the top of this laminate, an electrode was madethrough the deposition of an aluminum alloy, a product by KojundoChemical Laboratory, Co., Ltd., in which the weight ratio of Al to Liwas 99:1, on the fourth layer. The thickness of the electrode was 150nm.

The luminance and chromaticity of the obtained EL element were measuredwith the same method as in Working Example 3.

The results were that, when the voltage was 16 V and the current was17.5 mA, the luminance was 7,000 Cd/m², chromaticity X 0.35, andchromaticity Y 0.34. Also, a graph of the spectral radiance of thiswhite light-emitting compound that was measured with thespectroradiometer is shown in FIG. 20. From this graph, it is understoodthat the color of the emitted light was sufficiently white to the nakedeye.

Working Example 9

<Ethylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compoundrepresented by formula (12), the same compound as that obtained inWorking Example 1 was placed. 10.8 g (6.9×10⁻² mol) of iodoethane(C₂H₅I) and 200 ml of N,N-dimethyl-formamide (DMF) were added in thisorder to the compound. The mixture was heated to 150° C. in a siliconeoil bath and allowed to react for 20 hours. After the completion of thereaction, the bottle was cooled to the room temperature. Then, thereacted mixture was concentrated with an evaporator. The concentratedmixture was poured into ice water and further neutralized with sodiumhydroxide. The neutralized mixture was subjected to extraction withchloroform using a separatory funnel, and the extraction was carried outthree times. The extract was washed with water twice and then moistureincluded therein was removed with sodium sulfate. The washed and driedwas filtered, and concentrated and dried up with an evaporator. Theobtained solid was washed with petroleum ether, and dried in a vacuum.Liver brown powder was obtained. An IR chart of the liver brown powderis shown in FIG. 24.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (8.3×10⁻³ mol) of theproduct obtained in the preceding ethylation reaction, 8.0 g (4.2×10⁻²mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 25.

<Purification>

1.0 g of the brown powder obtained in the ring-closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated and dried up with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Light brown powder was obtained.

Working Example 10

<Butylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 10.8 g (7.6×10⁻² mol) ofn-butyl iodide (C₄H₉I) and 200 ml of N,N-dimethylformamide (DMF) wereadded in this order to the compound. The mixture was heated to 150° C.in a silicone oil bath and allowed to react for 20 hours. After thecompletion of the reaction, the bottle was cooled to the roomtemperature. Then, the reacted mixture was concentrated with anevaporator. The concentrated mixture was poured into ice water andfurther neutralized with sodium hydroxide. The neutralized mixture wassubjected to extraction with chloroform using a separatory funnel, andthe extraction was carried out three times. The extract was washed withwater twice and then moisture included therein was removed with sodiumsulfate. The washed and dried was filtered, and concentrated and driedup with an evaporator. The obtained solid was washed with petroleumether, and dried in a vacuum. Liver brown powder was obtained. An IRchart of the liver brown powder is shown in FIG. 26.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (7.5×10⁻³ mol) of theproduct obtained in the preceding butylation reaction, 7.2 g (3.7×10⁻²mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 27.

<Purification>

1.0 g of the brown powder obtained in the ring closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated and dried up with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Light brown powder was obtained.

Working Example 11

<Hexylation Reaction>

In a 500 ml pressure bottle, 5.0 g (8.0×10⁻³ mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 12.9 g (4.5×10⁻² mol) of hexyliodide (C₆H₁₃I) and 200 ml of N,N-dimethylformamide (DMF) were added inthis order to the compound. The mixture was heated to 150° C. in asilicone oil bath and allowed to react for 20 hours. After thecompletion of the reaction, the bottle was cooled to the roomtemperature. Then, the reacted mixture was concentrated with anevaporator. The concentrated mixture was poured into ice water andfurther neutralized with sodium hydroxide. The neutralized mixture wassubjected to extraction with chloroform using a separatory funnel, andthe extraction was carried out three times. The extract was washed withwater twice and then moisture included therein was removed with sodiumsulfate. The washed and dried was filtered, and concentrated and driedup with an evaporator. The obtained solid was washed with petroleumether, and dried in a vacuum. Liver brown powder was obtained. An IRchart of the liver brown powder is shown in FIG. 28.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (5.8×10⁻³ mol) of theproduct obtained in the preceding hexylation reaction, 6.6 g (3.5×10⁻²mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 29.

<Purification>

1.0 g of the brown powder obtained in the ring closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated and dried up with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Light brown powder was obtained.

Working Example 12

<Benzylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 17.1 g (7.6×10⁻² mol) ofbenzyl bromide (C₆H₅CH₂Br) and 200 ml of N,N-dimethylformamide (DMF)were added in this order to the compound. The mixture was heated to 150°C. in a silicone oil bath and allowed to react for 20 hours. After thecompletion of the reaction, the bottle was cooled to the roomtemperature. Then, the reacted mixture was concentrated with anevaporator. The concentrated mixture was poured into ice water andfurther neutralized with sodium hydroxide. The neutralized mixture wassubjected to extraction with chloroform using a separatory funnel, andthe extraction was carried out three times. The extract was washed withwater twice and then moisture included therein was removed with sodiumsulfate. The washed and dried was filtered, and concentrated and driedup with an evaporator. The obtained solid was washed with petroleumether, and dried in a vacuum. Liver brown powder was obtained. An IRchart of the liver brown powder is shown in FIG. 30.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (6.9×10⁻³ mol) of theproduct obtained in the preceding benzylation reaction, 5.2 g (2.7×10⁻²mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 31.

Working Example 13

<Dimethylbenzylation, or Xylylation Reaction>

In a 500 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 15.8 g (1.0×10⁻¹ mol) of2,4-dimethylbenzyl chloride (CH₃C₆H₃CH₃CH₂Cl) and 200 ml ofN,N-dimethylformamide (DMF) were added in this order to the compound.The mixture was heated to 150° C. in a silicone oil bath and allowed toreact for 20 hours. After the completion of the reaction, the bottle wascooled to the room temperature. Then, the reacted mixture wasconcentrated with an evaporator. The concentrated mixture was pouredinto ice water and further neutralized with sodium hydroxide. Theneutralized mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was carried out three times. Theextract was washed with water twice and then moisture included thereinwas removed with sodium sulfate. The washed and dried was filtered, andconcentrated and dried up with an evaporator. The obtained solid waswashed with petroleum ether, and dried in a vacuum. Liver brown powderwas obtained. An IR chart of the liver brown powder is shown in FIG. 32.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (6.9×10⁻³ mol) of theproduct obtained in the preceding dimethylbenzylation reaction, 6.0 g(3.2×10⁻² mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of there action, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 33.

<Purification>

1.0 g of the brown powder obtained in the ring closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated to dryness with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Light brown powder was obtained.

Working Example 14

<Naphthylation Reaction>

In a 500 ml pressure bottle, 5.0 g (8.0×10⁻³ mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 9.6 g (5.4×10⁻² mol) of1-chloromethylnaphthalene (C₁₀H₇CH₂Cl) and 200 ml ofN,N-dimethylformamide (DMF) were added in this order to the compound.The mixture was heated to 150° C. in a silicone oil bath and allowed toreact for 20 hours. After the completion of the reaction, the bottle wascooled to the room temperature. Then, the reacted mixture wasconcentrated with an evaporator. The concentrated mixture was pouredinto ice water and further neutralized with sodium hydroxide. Theneutralized mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was carried out three times. Theextract was washed with water twice, and then water included therein wasremoved with sodium sulfate. The washed and dried was filtered,concentrated to dryness with an evaporator. The obtained solid waswashed with petroleum ether, and dried in a vacuum. Liver brown powderwas obtained. An IR chart of the liver brown powder is shown in FIG. 34.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (6.0×10⁻³ mol) of theproduct obtained in the preceding naphthylation reaction, 6.9 g(3.6×10⁻² mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 35.

<Purification>

1.0 g of the brown powder obtained in the ring closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated and dried up with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Liver brown powder was obtained.

Working Example 15

<Anthrylation Reaction>

In a 500 ml pressure bottle, 5.0 g (8.0×10⁻³ mol) of the compound thathad the structure represented by formula (12), the same compound as thatobtained in Working Example 1 was placed. 8.6 g (5.4×10⁻² mol) of9-chloromethylanthracene (C₁₄H₇CH₂Cl) and 200 ml ofN,N-dimethylformamide (DMF) were added in this order to the compound.The mixture was heated to 150° C. in a silicone oil bath and allowed toreact for 20 hours. After the completion of the reaction, the bottle wascooled to the room temperature. Then, the reacted mixture wasconcentrated with an evaporator. The concentrated mixture was pouredinto ice water and further neutralized with sodium hydroxide. Theneutralized mixture was subjected to extraction with chloroform using aseparatory funnel, and the extraction was repeated twice more. Theextract was washed with water twice, and then moisture included thereinwas removed with sodium sulfate. The washed and dried was filtered, andconcentrated and dried up with an evaporator. The obtained solid waswashed with petroleum ether, and dried in a vacuum. Liver brown powderwas obtained. An IR chart of the liver brown powder is shown in FIG. 36.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (5.3×10⁻³ mol) of theproduct obtained in the preceding anthrylation reaction, 5.1 g (2.6×10⁻²mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown powder wasobtained. An IR chart of this brown powder is shown in FIG. 37.

<Purification>

1.0 g of the brown powder obtained in the ring closing reaction in 250ml of xylene, which was heated to 185° C. using a silicone oil bath, wasextracted for 24 hours with a Soxhlet abstractor. After the completionof the extraction, the extract was concentrated and dried up with anevaporator. The dried solid was washed with petroleum ether, and driedin a vacuum. Light brown powder was obtained.

Working Example 16

<Substituted-Methylbenzylation Reaction>

In a 1,000 ml pressure bottle, 10.0 g (1.6×10⁻² mol) of the compoundthat had the structure represented by formula (12), the same compound asthat obtained in Working Example 1 was placed. 2.3 g (1.6×10⁻² mol), thenumber of moles of which was the same as that of the compound (12), ofα-chloro-p-xylene and 500 ml of N,N-dimethylformamide (DMF) were addedin this order to the compound. The mixture was heated to 150° C. in asilicone oil bath and allowed to react for 20 hours. After thecompletion of the reaction, the bottle was cooled to the roomtemperature. Then, the reacted mixture was concentrated with anevaporator. The concentrated mixture was poured into ice water andfurther neutralized with sodium hydroxide. The neutralized mixture wassubjected to extraction with chloroform using a separatory funnel, andthe extraction was repeated twice more. The extract was washed withwater twice, and then moisture included therein was removed with sodiumsulfate. The washed and dried was filtered, and concentrated and driedup with an evaporator. The obtained solid was washed with petroleumether, and dried in a vacuum. Blue brown powder was obtained. An IRchart of the blue brown powder is shown in FIG. 38, and an NMR chartthereof in FIG. 39.

<Ring Closing Reaction>

In a 500 ml three-necked flask were placed 5.0 g (7.0×10⁻³ mol) of theproduct obtained in the preceding naphthylation reaction, 8.0 g(4.2×10⁻² mol) of p-toluenesulfonic acid monohydrate, and 200 ml ofo-dichlorobenzene. The mixture was placed in a silicone oil bath andheated to 160° C. with stirring. The reaction was allowed to continuefor 20 hours. After the termination of the reaction, the reacted mixturewas concentrated and dried up with an evaporator. The obtained solid waswashed with methyl alcohol that had been cooled to 5° C., acetone, andpetroleum ether in this order, and then vacuum dried. Brown solid wasobtained.

1.0 g of the obtained brown solid in 250 ml of xylene, which was heatedto 185° C. using a silicone oil bath, was extracted for 24 hours with aSoxhlet abstractor. After the completion of the extraction, the extractwas concentrated and dried up with an evaporator. The dried solid waswashed with petroleum ether, and dried in a vacuum. Light brown powderwas obtained. An IR chart of the light brown powder is shown in FIG. 40,and an NMR chart thereof in FIG. 41. This light brown powder wasidentified as a compound that had the structure represented by formula(1e) below.

<Luminescent Properties>

A sample solution was prepared by dissolving the white light-emittingcompound represented by formula (1e) in mixed xylene, so that theconcentration of the compound was 10 mg/L. This sample solution wasloaded in a model F-4500 spectrofluorophotometer, a product by ShimadzuCorporation, and the fluorescence spectrum of the solution was measuredunder the following conditions. The measured spectrum is shown in FIG.42.

Conditions of Measurement

-   Measuring mode: Wavelength scanning-   Exciting wavelength: 365 nm-   Wavelength at which the emission of fluorescence started: 400 nm-   Wavelength at which the emission of fluorescence ended: 700 nm-   Scanning speed: 1200 nm/min.-   Slit on the side of excitation: 5.0 nm-   Slit on the side of fluorescence emission: 5.0 nm-   Photomal voltage: 700 V

As understood from FIG. 42, the fluorescence of the white light-emittingcompound obtained in this example covers wavelengths of from 400 nm to700 nm.

Industrial Applicability

This invention can provide a luminescent compound capable of emittingwhite light by itself. The emission covers a visible light range of400-700 nm, and the luminance is not less than 2,000 Cd/m². Theinvention can also provide an illuminator and organic EL element capableof emitting white light by the employment of this compound. Theilluminator or element may be used for displays, illuminating devices,etc. that emit white light. Also, it maybe applied to advertisingapparatuses that are on in the dark, and road traffic signs.

1. A luminescent compound capable of emitting white light that has astructure represented by formula (1):

wherein R¹ is a hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; R² is a hydrogen atom, an alkylgroup, or an aryl or alkyl aryl group that may have at least onesubstituent, wherein two R²s may be the same or different from eachother; and R¹ and R² may be the same or different from each other.
 2. Aluminescent compound capable of emitting white light that has astructure represented by formula (2):

wherein R¹ is a hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; each of R³ and R⁴ is a hydrogen atom,an alkyl group, or an aryl or alkyl aryl group that may have at leastone substituent, wherein R³ and R⁴ may be the same or different fromeach other; and two R³s may be the same or different, and two R⁴s may bethe same or different. 3-15. (canceled)
 16. A layered article comprisingat least one luminescent compound selected from the group consisting of(A) a luminescent compound capable of emitting white light that has astructure represented by formula (1):

wherein R¹ is a hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; R² is a hydrogen atom, an alkylgroup, or an aryl or alkyl aryl group that may have at least onesubstituent, wherein two R²s may be the same or different from eachother; and R¹ and R² may be the same or different from each other, and(B) a luminescent compound capable of emitting white light that has astructure represented by formula (2):

wherein R¹ is a hydrogen atom, an alkyl group, or an aryl or alkyl arylgroup that may have at least one substituent, wherein two R¹s may be thesame or different from each other; each of R³ and R⁴ is a hydrogen atom,an alkyl group, or an aryl or alkyl aryl group that may have at leastone substituent, wherein R³ and R⁴ may be the same or different fromeach other; and two R³s may be the same or different, and two R⁴s may bethe same or different.
 17. The layered article according to claim 16, ina form of an organic EL element comprising a substrate, a pair ofelectrodes, and at least one light-emitting layer sandwiched between theelectrodes, wherein said light-emitting layer comprises at least one ofsaid luminescent compound, and wherein one of the electrodes is formedon the substrate.
 18. The layered article according to claim 16, in aform of an illuminator capable of emitting white light, wherein theilluminator comprises a substrate, a pair of electrodes, and at leastone light-emitting layer sandwiched between the electrodes, wherein saidlight-emitting layer comprises at least one of said luminescentcompound, and wherein one of the electrodes is formed on the substrate.19. The layered article according to claim 18, wherein the illuminatorcomprises a single light-emitting layer.
 20. The layered articleaccording to claim 18, wherein the illuminator (1) comprises two or morelight-emitting layers, at least one of which comprises said luminescentcompound, and (2) further comprises a hole-transporting layer and anelectron-transporting layer.
 21. The layered article according to claim17, wherein said light-emitting layer is prepared by dispersing saidluminescent compound in a high polymer.
 22. The layered articleaccording to claim 18, wherein said light-emitting layer is prepared bydispersing said luminescent compound in a high polymer.
 23. The layeredarticle according to claim 17, wherein said light-emitting layer isprepared by depositing said luminescent compound on said substrate. 24.The layered article according to claim 18, wherein said light-emittinglayer is prepared by depositing said luminescent compound on saidsubstrate.
 25. The layered article according to claim 17, wherein saidarticle has a planar shape.
 26. The layered article according to claim17, wherein said article has a tubular shape.
 27. The layered articleaccording to claim 18, wherein said article has a planar shape.
 28. Thelayered article according to claim 18, wherein said article has atubular shape.
 29. The layered article according to claim 19, whereinsaid article has a planar shape.
 30. The layered article according toclaim 19, wherein said article has a tubular shape.
 31. The layeredarticle according to claim 20, wherein said article has a planar shape.32. The layered article according to claim 20, wherein said article hasa tubular shape.